A styrenic polymer having syndiotactic configuration (hereinafter sometimes abbreviated as SPS) is excellent in heat resistance and chemical resistance but is poor in impact resistance and therefore, it has heretofore been limited in the scope of application usable as a construction material. In order to solve the problem, improvement have been made on the impact resistance of SPS, for example, by blending a rubbery elastomer and/or other thermoplastic resin with SPS. (Refer to Japanese Patent Application Laid-Open Nos. 257950/1987, 146944/1989, 182344/1989, 279944/1989 and 64140/1990.)
For example, there are available SPS containing a styrenic compound as a component and as a rubbery elastomer (refer to Japanese Patent Application Laid-Open No. 146944/1989), a SPS/rubber composition incorporated with a block or graft copolymer containing atactic polystyrene chain as a compatibilizer (refer to Japanese Patent Application Laid-Open No. 279944/1989), and a SPS/rubber composition incorporated with a poly(phenylene ether) (refer to Japanese Patent Application Laid-Open No. 279944/1989) and the like.
However, since there is used in the above-mentioned improved technique, a rubbery component or a block or graft copolymer containing atactic polystyrene chain as a compatibilizer for the purpose of improving the compatibility between SPS and the rubbery component that are incompatible with each other and enhancing the dispersibility and interfacial strength of the rubbery component, the problem still remains unsolved in that the working effect as the compatibilizer and the enhancement of impact resistance have still been insufficient. On the other hand, in the case of adding a large amount of a poly(phenylene ether) for the purpose of enhancing the impact resistance, the addition thereof inevitably brings about the deterioration of the resultant composition with respect to the hue and long-term heat resistance as well as the decrease in the crystallinity of the SPS.